<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        div{
            width: 100px;
            height: 100px;
            border:4px solid red;
            display: block;/*块级元素 竖着排 可设置大小*/
        }
        span{
            width: 100px;
            height: 100px;
            background-color:red;
            display: inline;/*行内元素 横着排 不可设置大小 可改成block*/
        }
        input,button{
            display: inline-block;/*行内块元素 横着排 也可竖着排 可设置大小 */
        }
        .d2:hover{
            /*文档流 页面多个元素按照自己显示模式特性有序排列*/
            /*脱离文档流*/
            display: none;/*悬停时隐藏元素*/}
    </style>
</head>
<body>
<div class="d1">111</div>
<div class="d2">222</div>
<div class="d3">333</div>
<hr>
<span>11111111</span>
<span>22222222</span>
<span>33333333</span>
<hr>
<button>121212121</button>
<input>


</body>
</html>